Blower



C. HUBRICH Feb. 18, 1964 BLOWER 2 Sheets-Sheet 1 Filed May 2, 1962 inlet 4 INVENTOR C'lrzlr/ A o q M M R i av /r4( -f;

Feb. 18, 1964 c. HUBRICH 2 BLOWER Filed May 2, 1962 2 Sheets-Sheet 2 IN VENTOR United States Patent 3,121,529 BLQJ'WER Christoph Hubrich, (litenbaeh (Maxim-Ember, Germany, assignor to Polysius G.m.b.E-l., Neubechum, Germany Filed May 2, 1962, Ser. No. $11,931 6 Claims. 2343-141) The present invention relates to a Roots blower. The customary Roots blower has in addition to its numerous advantages also two rather important and characteristic disadvantages, namely that of an isochronous compression and of a rather strongly oscillating pressure column in the feed conduit in View of the back flow from the pressure chamber into the opening up delivery chamber. When the rotary piston in view of a continuous rotation passes by the edge of the outlet and thereby establishes communication of the chamber containing air or another medium to be conveyed, in which the suction pressure prevails, with the pressure chamber, compressed air or discharge pressure will rush into the conveying chamber in a direction opposite to the flow and movement proper. This compressed air brings about a compression by intermixture. As a result thereof, the two above mentioned drawbacks occur which increases with increasing pressure ratio so that at a certain pressure ratioin practice approximately 1.8soon an upper limit of economy will be reached.

Various attempts have been made with different designs to obtain a pre-inflow into the chamber which is still closed and transports the medium to be conveyed, in order to overcome or reduce the above mentioned drawbacks. Thus, for instance, inclined discharge slots have been provided the edges of which no longer are being passed by by the rotary piston in a single position, i.e. in an infinitely short period of time. Instead, the movement of the rotary piston over said edges extends over a certain angle of rotation.

According to another heretofore made suggestion, the housing portion directly adjacent the outlet is not extended any longer centrally and at the same radius about the axis of rotation of the rotary piston but the said housing portion has been arranged in an offset manner and with a gradually increasing radius so that, so to speak, in the last portion of the conveying chamber transport the conveying chamber was filled more gradually by increased slot losses. in other words, with the above mentioned heretofore known suggested designs it was intended to obtain a more gradual overflow in order to prevent or reduce the sudden shock-like pressure equalization.

lowever, numerous tests have proved that the above advanced solutions are insutlicient. The reason for this is seen in the fact that the air employed for the overflow had as before to be withdrawn indirectly or directly from the pressure conduit and that, therefore, at the high rotary speed and the thus rather short time available for the overflow, the reduction of the overflow was so small that, for all practical purposes, in the pressure chamber no difference was noticeable over the customary sudden overflow.

It is also known with a Roots blower having two lemniscate or figure-eight rotary pistons to arrange rotary bodies in the last range or" the conveying chamber ahead of the outlet, said rotary bodies having a rotary valvelike contour of approximately semi-circular cross section. These rotary bodies are intended in addition to the rotary piston to compress the quantity conveyed into the chamber and to thereby avoid the pressure oscillations which may occur when opening the chambers toward the outlet side. With this construction, the aimed at advantage is obtained by complicating and thus in- "ice creasing the cost of the originally simple and low cost Roots blower.

It is, therefore, an object of the present invention to provide a Roots blower of the simple classic construction, which will overcome the above mentioned drawbacks.

It is another object of this invention to provide a Roots blower as set forth in the preceding paragraph, which will not require any additional rotary parts or a change in the simple ordinary conveyor chamber shape.

These and other objects and advantages of the invention will appear more clearly from the following specification in connection with the accompanying drawing in which FIGURE 1 diagrammatically illustrates a section through a Roots blower according to the invention showing the rotary pistons in their most important position.

FIGURE 2 illustrates in vertical section a portion of the housing, the outlet in this instance communicating with the resonance chamber through an annular overflow slot.

FIGURE 3 is a vertical section through a portion of the housing, while in this instance the overflow slot is interrupted by two partitions.

FIGURE 4 is a section through FIGURE 3 along the line lVlV thereof.

FIGURE 5 represents a horizontal section through the housing, while according to this modification the resonance chambers are separated from each other by partitions.

FZGURE 6 represents partly, in section, a further modification of the invention, in which the resonance chambers communicate through conduit means with a blower.

In order to assure that, already prior to reaching the discharge zone, an inner compression or pie-compression will be effected in the chamber transporting the medium to be conveyed, adjacent each rotary piston, it has been suggested according to the present invention to fill by overflow from a separate resonance chamber that portion of the conveying chamber which by means of a rotary piston is already cut oil from the suction chamer and is still separated from the pressure chamber proper and transports the medium to be conveyed. The said resonance chamber is connected to the pressure conduit by oscillation-free pipes. In this way, the over-flowing medium is not directly withdrawn from the pressure conduit.

It is also possible instead of the oscillation-free pipes to employ an annular overflow slot which extends over the entire circumference of the entire pressure conduit or may also be interrupted.

According to a further development of the invention, the annular resonance chamber may be subdivided so that each of the respective chambers formed by a rotary piston will be filled from a separate resonance chamber.

Referring now to the drawing in detail, the blower illustrated therein comprises a blower housing 1 with a chamber in which rotate the two rotary pistons 3 and 5. Adjacent the left-hand rotary piston 3 in the position of the drawing, there has just been formed a transporting chamber 2 transporting the medium to be conveyed. The blower is provided with an outlet or pressure conduit 9. When the left-hand rotary piston 3 by means of its upper edge separates chamber 2 from the inlet 4, its lower edge will pass over the overflow slot 6 on the left-hand side of the blower. The overflow slot 6 does, in contrast to heretofore known designs aiming at the realization of the same object, not directly lead into the pressure conduit 9 but into a resonance chamber '7 extending around pressure conduit 9. As will be evident from the drawing, the resonance chamber '7 communicates with the pressure conduit 9 through pipes t of relatively small cross section. These pipes d have been calculated as resonator or vibrator throats and in conformity with the known formulas or gas dynamics may be so designed that they will act as so-ca d oscillationfree pipes. When the rotary piston 3 thus passes beyond the left-hand overflow slot 6, chamber 2 will be filled from the resonance chamber 7 so as to establish the end condition of the conveyed medium. On the other hand, the resonance chamber 7 is in its turn not filled from the pressure conduit 9 in conformity with the sudden overfiow into the conveying chamber 2, but is gradually and continuously filled through the oscillation-free pipes 3. The harmful flow-back oscillations of the medium to be conveyed in the pressure chamber will thus be prevented and will be replaced by a completely harmless resonator oscillation in the resonance chamber 7. Thus, a considerably calmed down and almost stationary gas column will flow in the pressure conduit. This in turn also brings about a reduction in the discharge noise.

The above mentioned effect is further aided by the fact that the right-hand rotary piston 5 is just in the process of strongly displacing the medium to be conveyed into the discharge conduit and through the right-hand overflow slot =6 into the resonance chamber 7 when the left-hand chamber 2 is just in the process of being filled from said resonance chamber 7. Thus, it is by no means necessary to withdraw the total quantity of the medium required for filling the conveying chamber through the small pipes 8 from the pressure conduit 9 The operation on the ri-ght-hand blower side will, of course, be effected in a manner analogous to that described above in connection with the left-hand blower side. Whether the resonance chamber 7 is with a flange 1d directly cast to the blower housing 1 or whether it is connected to the pressure conduit 9 or blower housing in any other manner is, of course, a mere matter of design to be selected in conformity with the respective requirements and size of the blower.

It is, of course, to be understood that the present invention is, by no means, limited to the particular construction shown in the drawing but also comprises any modifications within the scope of the appended claims.

Thus, for instance, according to FIG. 2, the outlet 9 may communicate with the resonance chamber 7 through an annular overflow slot 8a. Furthermore, according to FIG. 3, the overflow slot 8b may be interrupted by partitions 11. According to a still further modification illustrated in FIG. 5, the resonance chambers 7 may be separated from each other by partitions 12.

Furthermore, while according to the drawing the resonance chamber communicates through the narrow pipes S with the pressure conduit, it is also possible to modify the blower according to the invention by having the resonance chamber or chambers not in communication with the pressure conduit but with a separate blower.

Such an arrangement is shown, for instance in FIG. 6, in which the resonance chambers 7 communicate through conduits 13 with a blower 14.

What I claim is: V

1. A Roots blower which comprises: a piston chamber having inlet means and outlet means, rotary pistons rotatably mounted in said piston chamber and operable periodically and successively to draw the medium to be compressed through said inlet means into conveying chambers confined by wall portions of said pistons and the respective adjacent wall portions of said piston chamber and to compress between said pistons the medium conveyed therebetween by said pistons and to discharge the thus compressed medium through said outlet means, auxiliary resonance chamber means, a source or" pressure medium of the same type as is to be delivered by said blower and at a pressure about the same as is developed by the blower, pipe means connecting said source with said auxiliary resonance chamber means, said pipe means being so dimensioned and arranged as to be oscillation free, and conduit means respectively leading from said auxiliary chamber means into said piston chamber and so located as to communicate with the respective conveying chamber only after the conveying chamber is shut oil by the respective piston from said inlet means and while the conveying chamber is still separated from said outlet means by the respective piston whereby pressure medium from said auxiliary chamber passes into said conveying chamber and increases the pressure in the conveying chamber to reduce pulsations in the medium discharged from the blower.

2. A Roots blower which comprises: a piston cham er having inlet means and outlet means, rotary pistons rotatably mounted in said piston chamber and operable periodically and successively to draw the medium to be com pressed through said inlet means into conveying chambers confined by wall portions of said pistons and the respective' adjacent wall portions of said piston chamber and to compress between said pistons the medium conveyed therebetween by said pistons and to discharge the thus compressed medium through said outlet means, auxiliary resonance chamber means, tubular means establishing communication between said outlet means and said auxiliary resonance chamber means, said tubular means being so dimensioned and arran ed as to be substantially oscillation free, and conduit means respectively leading from said auxiliary chamber means into said piston chamber at a point which is so located that the respective conveying chamber after being shut off by the respective pistonfrom said inlet means and while still separated from said outlet means by said piston communicates via said conduit means with said auxiliary chamber means whereby pressure medium from said auxiliary chamber means passes into said conveying chamber.

3. A Roots blower which comprises: a piston chamber having inlet means and outlet means, rotary pistons rotatably mounted in said piston chamber and operable periodically and successively to draw the medium to be compressed through said inlet means into conveying chambers confined by Wall portions of said piston and the respective adjacent wall portions of said piston chamber and to compress between said pistons the medium conveyed therebetween by said pistons and to discharge the thus compressed medium through said outlet means, auxiliary resonance chamber means surrounding said outlet means, annular slot means in the wall of said outlet means leading to said resonance chamber means so dimensioned and arranged as to establish substantially oscillation free communication between said outlet means and said auxiliary chamber means, and conduit means respectively leading from said auxiliary chamber means into said piston chamber at a point which is so located that the respective conveying chamber after being shut oil by the respective piston from said inlet means and while still separated from said outlet means by said piston communicates via said conduit means with said auxiliary chamber means whereby pressure medium from said auxiliary chamber means passes into said conveying chamber.

4-. 1A Roots blower which comprises: a piston chamber having inlet means and outlet means, rotary means rotatably mounted in said piston chamber and operable periodically and successively to draw the medium to be compressed through said inlet means into conveying chambers confined by wall portions of said pistons and the respective adjacent wall portions of said piston chamber and to compress between said pistons the medium conveyed thercbetween by said pistons and to discharge the thus compressed medium through said outlet means, auxiliary resonance chamber means subdivided into a plurality of individual chambers connected'with a source of pressure medium of the same type as it is tobe dclivered by said blower, a source of the said medium under pressure, first conduit means establishing communication between said source and said auxiliary chamber means and so dimensioned and arranged as to be oscillation free, and conduit means respectively leading from said auxiliary chamber means into said piston chamber at a point which is so located that the respective conveying chamber after being shut oil by the respective piston from said inlet means and while still separated from said outlet means by said piston communicates via said second conduit means with said auxiliary chamber means whereby pressure medium from said auxiliary chamber means passes into said conveying chamber.

5. A Roots blower which comprises: a piston chamber having inlet means and outlet means, rotary pistons rotatably mounted in said piston chamber and operable periodically and successively to draw the medium to be compressed through said inlet means into conveying chambers confined by wall portions of said pistons and the respective adjacent wall portions of said piston chamber and to compress between said pistons the medium conveyed therebetween by said pistons and to discharge the thus compressed medium through said outlet means, auxiliary chamber means, a separate source of pressure medium of the same type as it is to be delivered by said blower, first conduit means establishing communication between said separate source of pressure medium and said auxiliary chamber means, said first conduit means being so dimensioned and arranged as to be oscillation free, second conduit means leading from said auxiliary chamber means into said piston chamber at a point which is so located that the respective conveying chamber after being shut off by the respective piston from said inlet means while still being separated from said outlet means by said piston communicates via said second conduit means with said auxiliary chamber means whereby pressure medium from said auxiliary chamber means passes into said conveying chamber.

6. A Roots blower according to claim 1, in which said auxiliary chamber means is cast integrally with said piston chamber and surrounds said outlet means.

References Cited in the file of this patent UNITED STATES PATENTS 924,024 Wilkin June 8, 1909 1,058,646 Tomlinson Apr. 8, 1913 1,252,160 Pagel Jan. 1, 1918 2,028,414 Schneider June 21, 1936 2,259,027 De Zarate et al Oct. 14, 1941 2,489,887 Houghton Nov. 29, 1949 2,802,343 Seldon Aug. 13, 1957 FOREIGN PATENTS 1,224,547 France Feb. 8, 1960 1,232,429 France Apr. 25, 1960 678,867 Germany July 24, 1939 

1. A ROOTS BLOWER WHICH COMPRISES: A PISTON CHAMBER HAVING INLET MEANS AND OUTLET MEANS, ROTARY PISTONS ROTATABLY MOUNTED IN SAID PISTON CHAMBER AND OPERABLE PERIODICALLY AND SUCCESSIVELY TO DRAW THE MEDIUM TO BE COMPRESSED THROUGH SAID INLET MEANS INTO CONVEYING CHAMBERS CONFINED BY WALL PORTIONS OF SAID PISTONS AN THE RESPECTIVE ADJACENT WALL PORTIONS OF SAID PISTON CHAMBER AND TO COMPRESS BETWEEN SAID PISTONS THE MEDIUM CONVEYED THEREBETWEEN BY SAID PISTONS AND TO DISCHARGE THE THUS COMPRESSED MEDIUM THROUGH SAID OUTLET MEANS, AUXILIARY RESONANCE CHAMBER MEANS, A SOURCE OF PRESSURE MEDIUM OF THE SAME TYPE AS IS TO BE DELIVERED BY SAID BLOWER AND AT A PRESSURE ABOUT THE SAME AS IS DEVELOPED BY THE BLOWER, PIPE MEANS CONNECTING SAID SOURCE WITH SAID AUXILIARY RESONANCE CHAMBER MEANS, SAID PIPE MEANS BEING SO DIMENSIONED AND ARRANGED AS TO BE OSCILLATION FREE, AND CONDUIT MEANS RESPECTIVELY LEADING FROM SAID AUXILIARY CHAMBER MEANS INTO SAID PISTON CHAMBER AND SO LOCATED AS TO COMMUNICATE WITH THE RESPECTIVE CONVEYING CHAMBER ONLY AFTER THE CONVEYING CHAMBER IS SHUT OFF BY THE RESPECTIVE PISTON FROM SAID INLET MEANS AND WHILE THE CONVEYING CHAMBER IS STILL SEPARATED FROM SAID OUTLET MEANS BY THE RESPECTIVE PISTON WHEREBY PRESSURE MEDIUM FROM SAID AUXILIARY CHAMBER PASSES INTO SAID CONVEYING CHAMBER AND INCREASES THE PRESSURE IN THE CONVEYING CHAMBER TO REDUCE PULSATIONS IN THE MEDIUM DISCHARGED FROM THE BLOWER. 